1. Field of the Invention
The present invention generally relates to a vibration damper for a motor vehicle, which vibration damper can typically have a cylinder defining a substantially fluid filled chamber therewithin. A piston rod generally extends into the chamber through one end of the cylinder, and the piston rod preferably has a piston disposed thereon, which piston divides the chamber into two chamber portions. The chamber portion into which the piston is pushed during the insertion of the piston rod into the cylinder can be called the "compression" chamber, while the other chamber portion can be called the "rebound" chamber. In order to provide at least a portion of the damping function of the vibration damper, the piston can have fluid passages disposed therethrough and interconnecting the two chamber portions, whereby fluid flow through the passages is controlled by means of a damping valve.
More particularly, the present invention relates to a damping valve having a valve body with at least one admission channel, or flow passage for each direction of flow of fluid between the two chamber portions. Such admission channels essentially connect a top side and a bottom side of the damping valve body to one another. To provide a valve function, there can be a valve plate on a valve seat surface, whereby the valve plate can lift up off the valve seat surface in essentially one direction of flow, while in the opposite direction of flow, the valve plate can be pressed against the valve seat to close the passage. For the fluid flow passages permitting fluid to flow from the "rebound" chamber to the "compression" chamber, generally from the top side to the underside of the damping valve, there can preferably be a restriction for limiting the flow of fluid therethrough, or in other words, there can be a choke in the passage.
2. Background Information:
German Laid Open Patent Application No. 25 00 826, discloses valve designs of the general type as set forth above. In the valves disclosed therein, a relatively thick valve cover plate covers a ring groove having an internal contour. During assembly operations, this component must still be fed to the robot by hand.
Other known valve designs include coil spring valves of this type, in which valves the choke for the opposite damping valve is realized in the form of an additional disc inside the damping valve. In such a case, the use of a standard valve body which is already provided with non-choke openings is advantageous, because it makes it possible to standardize the damping valve. But the additional component which has the throttle openings and the above-mentioned weak points represents a disadvantage.
Unexamined French Patent Application FR-OS 2 061 905 discloses a valve with a very simple construction. The valve body consists of sheet metal, whereby all the holes are introduced by punching. The thin valve cover disc is penetrated by holes on an inside arc. The valve cover disc can be provided with a variable number of holes. But this valve disc is extraordinarily disadvantageous, since it must be installed in a defined position in relation to the valve body. The installation must once again be performed manually, since the disc does not have a design with a symmetry of rotation which would make it suitable for fully-automatic assembly operations. Because there are holes in the area of the maximum stresses, the durability of the component is severely restricted. There also exists a risk that the valve disc can twist out of position in relation to the valve body, either during the assembly process or during operation, and can result in at least a reduction of the passage cross section, if not a hydraulic blockage.